GEFS 0.4 is Live

I just released version 0.4

This is not a major step but it includes quite a few improvements and bug fixes.

- Improved muti-player mode, with a better extrapolation/interpolation.
- Current flight (and some preferences) is saved when exiting the sim, and restored when starting it up again.
- Orientable cockpit camera
- Improved players icon display on the map (orientation and altitude)
- A link generator so it is possible to link directly to GEFS and initialize a flight (plane, location).
- Updated flight models (the Piper CUB now has a bit more power, the DC3 a bit more grip)